1. Field of the Invention
This invention relates to an optical pickup apparatus for use in an optical disk apparatus in which various data, such as, audio data, video data and code data are recorded on and reproduced from a rotary disk by directing a laser beam.
2. Description of the Prior Art
FIG. 1 is a schematic perspective view showing a movable part of a prior art optical pickup apparatus. The movable part shown in FIG. 1 is that of an integrally driven optical pickup. Referring to FIG. 1, the prior art optical pickup apparatus includes an objective lens 31, a pickup driver part 32 having built-in optical elements including a semiconductor laser (referred to hereinafter as an LD), a magnet 33 for driving the pickup driver part 32, a plurality of wires 34a, 34b, 34c and 34d supporting the pickup driver part 32 so as to permit the operation of the pickup driver part 32 in the focusing and tracking directions and working also as signal lines for the transmission and reception of electrical signals between the pickup driver part 32 and an associated external circuit, a support plate 35 supporting the wires 34a to 34d to fix them in position, a plurality of auxiliary signal wires 36 compensating the function of the wires 34a to 34d when the wires 34a to 34d are insufficient to deal with all of the transmitted and received electrical signals, and a terminal plate 37 to which the auxiliary signal wires 36 are connected. Besides the optical pickup apparatus including the movable part of the optical pickup shown in FIG. 1, an optical pickup apparatus of the type in which the objective lens 31 only is arranged to move, and other optical elements are not arranged to move is frequently employed in this field. Nowadays, an optical pickup apparatus including a pickup movable part of integrally moving type as shown in FIG. 1 is most favorably employed in this field, because optically stable optical elements are integrally driven as a unit.
FIG. 2 is a block diagram showing the structure of a control circuit associated with the pickup driver part 32 of the prior art optical pickup apparatus shown in FIG. 1. In the control circuit shown in FIG. 2, it is supposed that a method of detecting astigmatism is based for the detection of a focusing error, and a method of three beam detection is based for the detection of a tracking error. Referring to FIG. 2, the control circuit includes a photo detector 41 receiving a laser beam reflected from a recording medium, a semiconductor laser 42, a pin diode (referred to hereinafter as a Pin) 43 for monitoring the output of the semiconductor laser 42, and a plurality of amplifiers 44a, 44b, 45a, 45b and 45c. Usually, the circuit elements lying on the left side of the dotted line 46 in FIG. 2 are mounted in the pickup driver part 32. However, in a high performance system in which self-adjustment is required, the circuit elements lying on the left side of the other dotted line 47 reassembled in the pickup driver part 32 in many cases, because signals, such as, signals FE+ and FE- are required before producing a focus error signal (referred to hereinafter as a signal FE). In this case, the pickup driver part 32 is connected to the associated external circuit by a total of eight signal lines, that is, signal lines for transmitting the signals FE+ and FE- respectively, signal lines for transmitting signals TE+ and TE- respectively for producing a tracking error signal (referred to hereinafter as a signal TE), a signal line extending from the LD 42, a signal line extending from the Pin 43, a signal line connected to ground GND, and a signal line connected to a voltage source Vcc. In the schematic diagram shown in FIG. 1, the number of wires 34a to 34d connected to the pickup driver part 32 is four. Therefore, the auxiliary signal wires 36 are utilized as the remaining four signal lines. Thus, when the control circuit controlling the pickup driver part 32 is divided along the dotted line 46 in FIG. 2, the total of the signal wires is seven, and the number of the required auxiliary signal wires 36 in FIG. 1 is three.
In the prior art optical pickup apparatus, the auxiliary signal wires 36 shown in FIG. 1 are provided in the form having a very small diameter or printed on a soft flexible printed circuit board (FPC) so as not to interfere with driving of the pickup driver part 32. However, in spite of the above contrivances, the adverse effect of the auxiliary signal wires 36 cannot be completely eliminated, and this leads to the problem that the desired control of the pickup driver part 32 cannot be satisfactorily achieved.